Method ProcessOne

libraries/lib-builtin-effects/SoundTouchBase.cpp:172–245

ProcessOne() takes a track, transforms it to bunch of buffer-blocks, and executes ProcessSoundTouch on these blocks

//ProcessOne() takes a track, transforms it to bunch of buffer-blocks,
//and executes ProcessSoundTouch on these blocks
bool SoundTouchBase::ProcessOne(soundtouch::SoundTouch *pSoundTouch,
   WaveChannel &orig, WaveTrack &out,
   sampleCount start, sampleCount end,
   const TimeWarper &warper)
{
   // ProcessStereo handles the stereo case instead.  This is a precondition
   // for Append:
   assert(out.NChannels() == 1);

   pSoundTouch->setSampleRate(
      static_cast<unsigned int>((orig.GetRate() + 0.5)));

   //Get the length of the buffer (as double). len is
   //used simple to calculate a progress meter, so it is easier
   //to make it a double now than it is to do it later
   auto len = (end - start).as_double();

   {
      //Initiate a processing buffer.  This buffer will (most likely)
      //be shorter than the length of the track being processed.
      Floats buffer{ orig.GetMaxBlockSize() };

      //Go through the track one buffer at a time. s counts which
      //sample the current buffer starts at.
      auto s = start;
      while (s < end) {
         //Get a block of samples (smaller than the size of the buffer)
         const auto block = std::min<size_t>(8192,
            limitSampleBufferSize(orig.GetBestBlockSize(s), end - s));

         //Get the samples from the track and put them in the buffer
         orig.GetFloats(buffer.get(), s, block);

         //Add samples to SoundTouch
         pSoundTouch->putSamples(buffer.get(), block);

         //Get back samples from SoundTouch
         unsigned int outputCount = pSoundTouch->numSamples();
         if (outputCount > 0) {
            Floats buffer2{ outputCount };
            pSoundTouch->receiveSamples(buffer2.get(), outputCount);
            out.Append(0, (samplePtr)buffer2.get(), floatSample, outputCount);
         }

         //Increment s one blockfull of samples
         s += block;

         //Update the Progress meter
         if (TrackProgress(mCurTrackNum, (s - start).as_double() / len))
            return false;
      }

      // Tell SoundTouch to finish processing any remaining samples
      pSoundTouch->flush();   // this should only be used for changeTempo - it dumps data otherwise with pRateTransposer->clear();

      unsigned int outputCount = pSoundTouch->numSamples();
      if (outputCount > 0) {
         Floats buffer2{ outputCount };